mtd: nand: more BB Detection refactoring and dynamic scan options

This is a revision to PATCH 2/2 that I sent. Link:
http://lists.infradead.org/pipermail/linux-mtd/2010-July/030911.html

Added new flag for scanning of both bytes 1 and 6 of the OOB for
a BB marker (instead of simply one or the other).

The "check_pattern" and "check_short_pattern" functions were updated
to include support for scanning the two different locations in the OOB.

In order to handle increases in variety of necessary scanning patterns,
I implemented dynamic memory allocation of nand_bbt_descr structs
in new function 'nand_create_default_bbt_descr()'. This replaces
some increasingly-unwieldy, statically-declared descriptors. It can
replace several more (e.g. "flashbased" structs). However, I do not
test the flashbased options personally.

How this was tested:

I referenced 30+ data sheets (covering 100+ parts), and I tested a
selection of 10 different chips to varying degrees. Particularly, I
tested the creation of bad-block descriptors and basic BB scanning on
three parts:

ST NAND04GW3B2D, 2K page
ST NAND128W3A, 512B page
Samsung K9F1G08U0A, 2K page

To test these, I wrote some fake bad block markers to the flash (in OOB
bytes 1, 6, and elsewhere) to see if the scanning routine would detect
them properly. However, this method was somewhat limited because the
driver I am using has some bugs in its OOB write functionality.

Signed-off-by: Brian Norris <norris@broadcom.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

1 files changed, 72 insertions, 55 deletions

diff --git a/drivers/mtd/nand/nand_bbt.c b/drivers/mtd/nand/nand_bbt.c
index ec1700e..469de17 100644
--- a/drivers/mtd/nand/nand_bbt.c
+++ b/drivers/mtd/nand/nand_bbt.c
@@ -93,6 +93,28 @@ static int check_pattern(uint8_t *buf, int len, int paglen, struct nand_bbt_desc
 			return -1;
 	}
 
+	/* Check both positions 1 and 6 for pattern? */
+	if (td->options & NAND_BBT_SCANBYTE1AND6) {
+		if (td->options & NAND_BBT_SCANEMPTY) {
+			p += td->len;
+			end += NAND_SMALL_BADBLOCK_POS - td->offs;
+			/* Check region between positions 1 and 6 */
+			for (i = 0; i < NAND_SMALL_BADBLOCK_POS - td->offs - td->len;
+					i++) {
+				if (*p++ != 0xff)
+					return -1;
+			}
+		}
+		else {
+			p += NAND_SMALL_BADBLOCK_POS - td->offs;
+		}
+		/* Compare the pattern */
+		for (i = 0; i < td->len; i++) {
+			if (p[i] != td->pattern[i])
+				return -1;
+		}
+	}
+
 	if (td->options & NAND_BBT_SCANEMPTY) {
 		p += td->len;
 		end += td->len;
@@ -124,6 +146,13 @@ static int check_short_pattern(uint8_t *buf, struct nand_bbt_descr *td)
 		if (p[td->offs + i] != td->pattern[i])
 			return -1;
 	}
+	/* Need to check location 1 AND 6? */
+	if (td->options & NAND_BBT_SCANBYTE1AND6) {
+		for (i = 0; i < td->len; i++) {
+			if (p[NAND_SMALL_BADBLOCK_POS + i] != td->pattern[i])
+				return -1;
+		}
+	}
 	return 0;
 }
 
@@ -397,12 +426,10 @@ static int create_bbt(struct mtd_info *mtd, uint8_t *buf,
 
 	if (bd->options & NAND_BBT_SCANALLPAGES)
 		len = 1 << (this->bbt_erase_shift - this->page_shift);
-	else {
-		if (bd->options & NAND_BBT_SCAN2NDPAGE)
-			len = 2;
-		else
-			len = 1;
-	}
+	else if (bd->options & NAND_BBT_SCAN2NDPAGE)
+		len = 2;
+	else
+		len = 1;
 
 	if (!(bd->options & NAND_BBT_SCANEMPTY)) {
 		/* We need only read few bytes from the OOB area */
@@ -1092,41 +1119,6 @@ int nand_update_bbt(struct mtd_info *mtd, loff_t offs)
  * while scanning a device for factory marked good / bad blocks. */
 static uint8_t scan_ff_pattern[] = { 0xff, 0xff };
 
-static struct nand_bbt_descr smallpage_memorybased = {
-	.options = 0,
-	.offs = NAND_SMALL_BADBLOCK_POS,
-	.len = 1,
-	.pattern = scan_ff_pattern
-};
-
-static struct nand_bbt_descr smallpage_scan2nd_memorybased = {
-	.options = NAND_BBT_SCAN2NDPAGE,
-	.offs = NAND_SMALL_BADBLOCK_POS,
-	.len = 2,
-	.pattern = scan_ff_pattern
-};
-
-static struct nand_bbt_descr largepage_memorybased = {
-	.options = 0,
-	.offs = NAND_LARGE_BADBLOCK_POS,
-	.len = 1,
-	.pattern = scan_ff_pattern
-};
-
-static struct nand_bbt_descr largepage_scan2nd_memorybased = {
-	.options = NAND_BBT_SCAN2NDPAGE,
-	.offs = NAND_LARGE_BADBLOCK_POS,
-	.len = 2,
-	.pattern = scan_ff_pattern
-};
-
-static struct nand_bbt_descr lastpage_memorybased = {
-	.options = NAND_BBT_SCANLASTPAGE,
-	.offs = 0,
-	.len = 1,
-	.pattern = scan_ff_pattern
-};
-
 static struct nand_bbt_descr smallpage_flashbased = {
 	.options = NAND_BBT_SCAN2NDPAGE,
 	.offs = NAND_SMALL_BADBLOCK_POS,
@@ -1175,6 +1167,43 @@ static struct nand_bbt_descr bbt_mirror_descr = {
 	.pattern = mirror_pattern
 };
 
+#define BBT_SCAN_OPTIONS (NAND_BBT_SCANLASTPAGE | NAND_BBT_SCAN2NDPAGE | \
+		NAND_BBT_SCANBYTE1AND6)
+/**
+ * nand_create_default_bbt_descr - [Internal] Creates a BBT descriptor structure
+ * @this:	NAND chip to create descriptor for
+ *
+ * This function allocates and initializes a nand_bbt_descr for BBM detection
+ * based on the properties of "this". The new descriptor is stored in
+ * this->badblock_pattern. Thus, this->badblock_pattern should be NULL when
+ * passed to this function.
+ *
+ * TODO: Handle other flags, replace other static structs
+ *        (e.g. handle NAND_BBT_FLASH for flash-based BBT,
+ *             replace smallpage_flashbased)
+ *
+ */
+static int nand_create_default_bbt_descr(struct nand_chip *this)
+{
+	struct nand_bbt_descr *bd;
+	if (this->badblock_pattern) {
+		printk(KERN_WARNING "BBT descr already allocated; not replacing.\n");
+		return -EINVAL;
+	}
+	bd = kzalloc(sizeof(*bd), GFP_KERNEL);
+	if (!bd) {
+		printk(KERN_ERR "nand_create_default_bbt_descr: Out of memory\n");
+		return -ENOMEM;
+	}
+	bd->options = this->options & BBT_SCAN_OPTIONS;
+	bd->offs = this->badblockpos;
+	bd->len = (this->options & NAND_BUSWIDTH_16) ? 2 : 1;
+	bd->pattern = scan_ff_pattern;
+	bd->options |= NAND_BBT_DYNAMICSTRUCT;
+	this->badblock_pattern = bd;
+	return 0;
+}
+
 /**
  * nand_default_bbt - [NAND Interface] Select a default bad block table for the device
  * @mtd:	MTD device structure
@@ -1217,20 +1246,8 @@ int nand_default_bbt(struct mtd_info *mtd)
 	} else {
 		this->bbt_td = NULL;
 		this->bbt_md = NULL;
-		if (!this->badblock_pattern) {
-			if (this->options & NAND_BBT_SCANLASTPAGE)
-				this->badblock_pattern = &lastpage_memorybased;
-			else if (this->options & NAND_BBT_SCAN2NDPAGE)
-				this->badblock_pattern = this->badblockpos ==
-					NAND_SMALL_BADBLOCK_POS ?
-					&smallpage_scan2nd_memorybased :
-					&largepage_scan2nd_memorybased;
-			else
-				this->badblock_pattern = this->badblockpos ==
-					NAND_SMALL_BADBLOCK_POS ?
-					&smallpage_memorybased :
-					&largepage_memorybased;
-		}
+		if (!this->badblock_pattern)
+			nand_create_default_bbt_descr(this);
 	}
 	return nand_scan_bbt(mtd, this->badblock_pattern);
 }